Högimpedansingång

Högimpedansingång refers to an input stage in an electronic circuit designed to present a very high impedance to the signal source. This is crucial for minimizing the loading effect of the measuring or amplifying circuit on the source. When a circuit has a low input impedance, it draws significant current from the source, which can alter the voltage or behavior of the source itself, leading to inaccurate measurements or distorted signals. A high impedance input, conversely, draws very little current, ensuring that the signal from the source is passed through with minimal disturbance.

This principle is commonly employed in various electronic applications. For instance, in audio amplifiers, a high impedance microphone input prevents the microphone's output from being unduly loaded, preserving its natural sound quality. In measurement instruments like oscilloscopes and multimeters, high impedance inputs are essential for accurately measuring voltages without affecting the circuit under test. Operational amplifiers (op-amps) are frequently configured with high impedance inputs, often through the use of buffer stages or specialized input transistors like JFETs or MOSFETs. The goal is always to achieve a faithful transfer of the signal from the source to the subsequent stages of the circuit.